1. Field of Invention
The present invention relates to electrical input devices for computer systems, specifically to an improvement to existing pointing devices such as mice and pointing sticks.
2. Description of Prior Art
Pointing devices, such as mice and pointing sticks, are widely used with modem computer systems. Pointing devices translate input from an operator into electrical control signals. An input can be in many forms. It can be, for example, the distance of a movement, or the strength of an applied force, or the duration of an event, etc. Regarding the output signals, pointing devices are used for producing two types of control signals for computer systems, namely, “positional signals” and “non-positional signals”. Positional signals are used to control positions or displacements of a computer-controlled target, such as a cursor or a robot. Non-positional signals are used to select, or to change properties of, the computer-controlled target.
FIG. 1 shows a prior-art computer system using a mouse 22 as a pointing device. Moving the mouse produces positional signals. These signals are used to control the position of a cursor 16 on a screen 14. On the other hand, clicking buttons 24 produces non-positional signals, and these signals are used for tasks such as the selection of a menu item.
A coordinate system 18, with axes marked by lower-case letters x, y, and z, is referred to as the “input space”. Another coordinate system 20, with axes marked by upper-case letters X, Y, and Z, is referred to as the “output space”. Pointing devices (e.g., mouse 22) are operated in the input space (e.g., the space near mouse 22), while targets (e.g., cursor 16) are moved in the output space (e.g., screen 14). For one aspect, the mouse acts as a proxy for the cursor. That is, the mouse's movements in input space 18 are mapped into movements of the cursor in output space 20. When a target's 3D movements are limited by a 2D display device such as the screen, the Z-axis movement may be virtually represented as “zoom in” or “zoom out” of the target's image on the screen.
When a pointing device is positioning a target, a maximum of six degrees of freedom (DOF) can be controlled by the positional control signals. Three of them are translational movements on the x, y, and z axes, which represents a target's position change projected onto these axes. The others are rotational movements about the x, y, and z axes, which control a target's orientation with respect to these axes. Each DOF requires an independent control signal channel from the pointing device. The information contained in the signals from each channel, such as their magnitude, reflects the amplitude of the user input, such as the distance a mouse has been moved or the pressure that has been exerted on a pointing stick by pushing it.
With regard to mapping a channel of positional signals to a target's movement in one DOF, pointing devices can be classified into “isometric” and “isotonic” devices. An isotonic pointing device maps the magnitude of the signals to the distance of a target's movement. An isometric pointing device, on the other hand, maps the magnitude of the signals to the speed with which a target moves. These mappings may not necessarily be linear. A conventional mouse is an example of an isotonic pointing device. A conventional pointing stick is an example of an isometric pointing device.
Mice are well known pointing devices. Operating a mouse requires a relatively large and flat working space. This requirement renders mice unsuitable for portable computers. Also, when moving a cursor over a long distance on the screen, one often needs to lift and reposition the mouse body repeatedly. This problem is sometimes referred to as “clutching”.
Pointing sticks are also commonly seen pointing devices. Compared to mice, pointing sticks are isometric pointing devices. They are mounted on fixed bases and require less working space to operate. Also, pointing sticks do not suffer from the clutching problem. For these reasons, they can be used in portable computers.
However, pointing sticks can be difficult to use. A pointing stick employs a miniaturized stick operated by a finger. The tip of the stick is generally tiny and thus difficult to contact and move by the operating finger. Also, the stick cannot provide proper rest support to the finger. Moreover, because of its small size, a pointing stick cannot be integrated with buttons. To produce non-positional signals, a pointing stick requires additional buttons in a different location. This means that fingers have to be moved forth and back in order to perform “point and click” operations.
A device disclosed in U.S. Pat. No. 6,121,954 to Seffernick, 2000, is an improved isometric pointing device. The device has an integrated z-axis sensor, which detects the movement of a finger-operated element along the z axis and produces corresponding signals. Seffemick claims that the signal produced by the z-axis sensor can be used to simulate button-clicks, so the devices can perform “point and click” simultaneously. However, because there is only one movable element to interact with the z-axis sensor, the device can only simulate a single button. In other words, it cannot be used for an application that needs multiple-button inputs (e.g. “left click”, “right click”, etc.).
U.S Pat. No. 6,326,948 to Kobachi, et al., 2001, describes another device integrated with a z-axis sensor. It suggests that signals produced by the z-axis sensor can be used to control a target's movement along the axis. One shortcoming of this approach is that the sensor will only respond to a finger's downward “push”, but not the finger's upward “lift”. Hence, an operator can only move a target in one direction along the Z axis.
Another isometric input device, disclosed in U.S. Pat. No. 6,246,391 to Ong, 2001, employs a dangling ball connected to a frame via elastic springs. An operator twists and moves the ball from the input space to control a cursor's movement in the output space. One shortcoming of the device is its large size. It also requires a large amount of space to operate. As a result, the device cannot be integrated into portable computers. Ong suggests that buttons be integrated into the ball so the operator can “point and click” at the same time. However, the operator has to grasp the ball by using some fingers and click on the buttons by using some other fingers. In other words, the device cannot do both “point and click” using the same fingers, and is therefore less effective. Moreover, ergonomic factors, such as providing rest support to the operating fingers, are not well addressed in these devices.
Yet another input device, disclosed in U.S. patent application publication 2002/0,039,093 to Healey, published Apr. 4, 2002, allows a user to operate on a “control member” using fingers. The control member is basically a mouse mounted on top of a pointing stick. Similar to the Ong device above, it is difficult to move the control member by solely using the button-clicking fingers. This is due to lack of proper finger-engaging constructs. Also, the device is limited to providing positional control signals for two DOFs only.
Lastly, normal pointing devices, like mice or pointing sticks, provide only positional controls of the target over two DOFs. Devices offering control of a target for more than two DOFs, such as the one disclosed in U.S. Pat. No. 4,811,608 to Hilton, 1989, are complex and expensive to build. Many of them are awkward to use.
Objects and Advantages
Accordingly, several objects and advantages of the invention are:
to provide a pointing device of compact size that requires minimal space to operate and can be operated by using fingers of a hand only, which renders it suitable for use with portable computers;
to provide a pointing device that can be integrated with buttons; the device therefore can produce both positional and non-positional signals;
to provide a pointing device that is able to control a target's position in an output space over a maximum of six degrees of freedom; and
to provide an ergonomic pointing device that provides proper feedback and rest support to the operator's fingers.
Other objects and advantages are:
to provide a device which uses existing technologies and off-the-shelf components, so that manufacturing the device is less expensive; and
to provide a device that can be integrated with many types of input elements, including buttons, wheels, pressure sensors, tablets, miniaturized pointing sticks, miniaturized track balls, etc, whereby the device is suited to a wide range of applications.
Further objects and advantages will become apparent from a consideration of the drawings and ensuing description.